#include "bits/stdc++.h"
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair <ll,ll> pll;
typedef pair <int,int> pii;
typedef pair <int,pii> piii;

#define forr(_a,_b,_c) for(int _a = (_b); _a <= int (_c); ++_a)
#define ford(_a,_b,_c) for(int _a = (_b) + 1; _a --> int (_c);)
#define forf(_a,_b,_c) for(int _a = (_b); _a < int (_c); ++_a)
#define st first
#define nd second
#define pb push_back
#define mp make_pair
#define all(x) begin(x),end(x)
#define mask(i) (1LL << (i))
#define bit(x, i) (((x) >> (i)) & 1)
#define bp __builtin_popcountll
#define file "test"

template<class X, class Y>
    bool minz(X &x, const Y &y) {
        if (x > y) {
            x = y;
            return true;
        } return false;
    }
template<class X, class Y>
    bool maxz(X &x, const Y &y) {
        if (x < y) {
            x = y;
            return true;
        } return false;
    }

const int N = 5e5 + 5;
const ll oo = (ll) 1e16;
const ll mod = 1e9 + 7; // 998244353;

int n, m, u, v, res, f[N], gg[N];
vector <int> a[N], ra[N];


void dfs2 (int u){
    f[u] = 1;
    for (int v : ra[u])
    if (!f[v])
        dfs2(v);
}

int main(){
    ios_base::sync_with_stdio(0); cin.tie(0);
    #ifdef hqm
        freopen(file".inp", "r", stdin); freopen(file".out", "w", stdout);
    #endif

    cin >> n >> m;

    forr (i, 1, m){
        cin >> u >> v;
        a[u].pb(v);
        ra[v].pb(u);
    }

    dfs2(n);
    
    gg[1] = 1;

    forr (i, 1, n){
        if (!gg[i]) continue;

        int cnt = 0;
        
        for (int v : a[i]){
            cnt += f[v];    
            gg[v] = 1;
        }
        
        if (cnt) res += cnt - (i != 1);
    }

    cout << res << "\n";

    return 0;
}
/*



*/